1. Field of the Invention
The invention relates to an electrodeposition process and somewhat more particularly to an electrolytic process involving the use of a fused salt electrolyte.
2. Prior Art
When a desired metal or alloy, such as titanium, is electrodeposited by prior art fused salt electrolytic methods, the deposited metal or alloy thereof is generally obtained only in a fused state or as a powder, granulated crystals, dendrite or sponge. Accordingly, we have proposed various electrodeposition processes in which a novel fused salt electrolytic bath is used so that an electrodeposited material or alloy can be obtained in a desired shape, such as a flat plate, a compact ingot, a cake or the like having a desired thickness which can be readily processed, such as by rolling or forming operations without requiring remelting, etc. (J. of Metals, Vol. 27, No. 11, November 1975, pp. 18-23). In addition, we have proposed electrodeposition processes such as disclosed in Japanese Patent Application Nos. 131970/1974, which corresponds to U.S. Pat. No. 4,016,052 and 107500/1974, which corresponds to U.S. Pat. No. 4,049,507, as well as in Japanese Pat. No. 726754, which corresponds to U.S. Pat. No. 3,662,047.
In the above described electrolysis methods, the composition of the fused salts in a fused salt electrolytic bath is important. However, it is also important to increase the concentration of a raw-material component salt of a desired metal or alloy to be electrodeposited, preferably at least around the electrodeposition surface, i.e., the cathode surface.
In order to electrodeposit a desired metal or allow, for example, titanium, from a fused chloride salt electrolytic bath so that the deposited metal surface is maintained relatively homogeneous, smooth and flat, theory suggests that it may be advisable to maintain a lower valency salt, for example, of titanium (i.e., TiCl.sub.2 and/or TiCl.sub.3) at a concentration in the vicinity of the cathode greater than the solubility of such lower valency salt in the electrolytic bath at the electrolytic temperature.
However, the above theoretical suggestion is of no particular importance in the prior art processes since the primary object thereof was merely to produce an electrodeposited metal as granulated crystals, powders or as a sponge. Nevertheless, in order to achieve an electrodeposition process in which a desired metal, for example, titanium, is electrodeposited from a fused chloride salt electrolytic bath as a deposit which has substantially homogeneous smooth flat surfaces, it appears necessary to increase the concentration of a lower valency salt of a desired metal contained within a fused electrolytic bath, as compared with presently known fused salt electrolytic baths but no process for adjusting the concentration of certain components within such a bath is presently known.